For reduced weights or increased sizes, steel structures such as automobiles, construction machines, bridges, and architectural buildings need to use high tensile strength steel called a high tensile strength material to reduce the board thicknesses or cross-sectional areas of members thereof. However, disadvantageously, the reduced board thicknesses or cross-sectional areas of the members may reduce the rigidity thereof, causing the members to be significantly deformed, that is, deflected, under an external force. This may prevent the safety of steel structures from being ensured. Thus, there has been a strong demand for a technique to achieve a consistent reduction in both the weight and deflection of structural members.
Among techniques to reduce the deflection of structural members, a technique is widely known in which a reinforcing plate called a rib is attached to a crossing portion of the structural member. Furthermore, Patent Literature 1 discloses a technique to bend an end of a plate-like reinforcing plate into a U or V shape to improve the proof stress and fatigue performance of the structural member. Additionally, Patent Literature 2 discloses a technique to define the angle between a U- or V-shaped reinforcing material and a structural member and the width of the combination of the reinforcing material and structural member, to improve the proof stress and fatigue performance of the structural member.
Furthermore, Patent Literature 3 discloses a coupled structure including a structural member having a hollow cross section with bulkheads and a coupling member with an opening end into which the structural member is inserted.
Additionally, Patent Literature 4 discloses a joining structure in which a columnar structural member is joined to a second structural member. A plate-like reinforcing material is welded to the columnar structural member and second structural member joined together to reinforce the junction between the structural members. The reinforcing material includes a bent portion that is U- or V-shaped along a surface of the structural member, and a ring-like opening.